In reply to Matt.

Remember that review scheme in a serp is only tied to a secondary page and not the home page of the website. You will never see star ratings on a home page. You will only see star ratings on a langing page. So, while anyone can download the WP Reviews plugin and assign start ratings and fake reviews to their site, the stars will only be visible on a landing page and not the home page. Landing pages are usually marketed via pay per click. I don't find a lot of landing pages with star ratings in a Google search. I think they must know that while star ratings are cool, they are not a ranking signal.